Editing Sponge (section)

==== Sexual ====

Most sponges are [[hermaphrodite]]s (function as both sexes simultaneously), although sponges have no [[gonad]]s (reproductive organs). Sperm are produced by [[choanocyte]]s or entire choanocyte chambers that sink into the [[mesohyl]] and form spermatic [[cyst]]s while eggs are formed by transformation of [[archeocyte]]s, or of choanocytes in some species. Each egg generally acquires a [[yolk]] by consuming "nurse cells". During spawning, sperm burst out of their cysts and are expelled via the [[osculum]]. If they contact another sponge of the same species, the water flow carries them to choanocytes that engulf them but, instead of digesting them, metamorphose to an [[ameboid]] form and carry the sperm through the mesohyl to eggs, which in most cases engulf the carrier and its cargo.<ref name="Ruppert_2004"/>{{rp|77}}

A few species release fertilized eggs into the water, but most retain the eggs until they hatch. By retaining the eggs, the parents can transfer symbiotic microorganisms directly to their offspring through [[vertical transmission]], while the species who release their eggs into the water has to acquire symbionts horizontally (a combination of both is probably most common, where larvae with vertically transmitted symbionts also acquire others horizontally).<ref>{{cite journal |last1=Díez-Vives |first1=Cristina |last2=Koutsouveli |first2=Vasiliki |last3=Conejero |first3=Maria |last4=Riesgo |first4=Ana |title=Global patterns in symbiont selection and transmission strategies in sponges |journal=Frontiers in Ecology and Evolution |volume=10 |date=26 October 2022 |issn=2296-701X |doi=10.3389/fevo.2022.1015592 |doi-access=free}}</ref><ref>{{cite journal |last1=Carrier |first1=Tyler J. |last2=Maldonado |first2=Manuel |last3=Schmittmann |first3=Lara |last4=Pita |first4=Lucía |last5=Bosch |first5=Thomas C. G. |last6=Hentschel |first6=Ute |title=Symbiont transmission in marine sponges: reproduction, development, and metamorphosis |journal=BMC Biology |volume=20 |issue=1 |pages=100 |date=May 2022 |pmid=35524305 |pmc=9077847 |doi=10.1186/s12915-022-01291-6 |doi-access=free }}</ref> There are four types of larvae, but all are lecithotrophic (non-feeding) balls of cells with an outer layer of cells whose [[flagella]] or [[cilia]] enable the larvae to move. After swimming for a few days the larvae sink and crawl until they find a place to settle. Most of the cells transform into archeocytes and then into the types appropriate for their locations in a miniature adult sponge.<ref name="Ruppert_2004"/>{{rp|77}}<ref>{{cite journal |last1=Riesgo |first1=Ana |last2=Taboada |first2=Sergio |last3=Sánchez-Vila |first3=Laura |last4=Solà |first4=Joan |last5=Bertran |first5=Andrea |last6=Avila |first6=Conxita |title=Some Like It Fat: Comparative Ultrastructure of the Embryo in Two Demosponges of the Genus Mycale (Order Poecilosclerida) from Antarctica and the Caribbean |journal=PLOS ONE |volume=10 |issue=3 |date=18 March 2015 |issn=1932-6203 |pmid=25785444 |pmc=4365022 |doi=10.1371/journal.pone.0118805 |doi-access=free |page=e0118805|bibcode=2015PLoSO..1018805R }}</ref>

[[Glass sponge]] embryos start by dividing into separate cells, but once 32&nbsp;cells have formed they rapidly transform into larvae that externally are [[ovoid]] with a band of [[cilia]] round the middle that they use for movement, but internally have the typical glass sponge structure of spicules with a cobweb-like main [[syncitium]] draped around and between them and [[choanosyncytia]] with multiple collar bodies in the center. The larvae then leave their parents' bodies.<ref>{{cite journal |last=Leys |first=S. P. |title=Embryogenesis in the glass sponge Oopsacas minuta: Formation of syncytia by fusion of blastomeres |journal=Integrative and Comparative Biology |volume=46 |issue=2 |date=16 February 2006 |issn=1540-7063 |doi=10.1093/icb/icj016 |pages=104–117|pmid=21672727 }}</ref>